A cold frame is an easy DIY structure that acts like a mini-greenhouse, trapping heat and protecting plants from frost. By building and using a cold frame, you can start seedlings earlier in spring and grow cool-weather crops later into fall.
Materials & Tools
- Untreated lumber (2×4 or timbers) for the frame
- Transparent lid material (acrylic sheet, old window, or polycarbonate panel)
- Screws or exterior-grade nails
- Hinges and latch for lid attachment
- Measuring tape, saw, drill, screwdriver
Step-by-Step Construction
- Site Selection: Choose a south-facing, level spot with good drainage.
- Build the Frame:
- Cut four boards to form a box sized to your lid (e.g., 1 m × 0.6 m).
- Assemble into a rectangle, attaching boards with screws.
- Attach the Lid:
- Secure hinges along the back edge so the lid can open for ventilation.
- Install a latch on the front to keep it closed.
- Position and Prep:
- Place on ground; line interior with landscaping fabric to suppress weeds.
- Add 5–10 cm of soil or potting mix.
Seasonal Use
- Spring: Sow early lettuce, spinach, kale; cover at night until soils warm.
- Fall: Transplant seedlings of fall greens; close lid on frosty nights.
- Ventilation: Open lid on warm days to prevent overheating and ensure airflow.